Centrifugal classification apparatus



Jan. 29, 1957 H. G. LYKKEN 2,77

CENTRIFUGAL CLASSIFICATION APPARATUS Filed Sept. 10, 1951 4 Sheets-Sheet l JNVENTOR. HENRY G. LYKKE/V Jan. 29, 1957 H.. G. LYKKEN CENTRIFUGAL CLASSIFICATION APPARATUS 4 Sheets-Sheet 2 Filed Sept. 10, 1951 WIIIIILQ'IIIII IWIIIIIIIIIII IIIIIII.

m m ML V mG 4 ATTORNEYS Jan. 29, 1957 LYKKEN 2,779,467

CENTRIFUGAL CLASSIFICATION APPARATUS Filed Sept. 10, 1951 4 Sheets-Sheet 5 A ENTOR. 'I

United StatesPatent O r CENTRIF-UGAL .CLASSIFICATION APPARATUS Henry G. Lykken, Minneapolis, Minn., assignor to The MlcrocyclomatCo Minneapolis, Minn., a corporation of Delaware -Application September 10, 1951,.Serial No. 245,816

12 Claims. (Cl.209--139) This invention relates to rotary classifiers for separating solid particles of difierent sizes while they are carried in a .gaseous fluid, and particularly to a rotary classifier which .may be built in conjunction with or as a part of a rotary grinding machine. g It is an object of the invention toprovidea classifier for the separation of varying sizes of solid particles whereby the particle size segregation and selection is carried out on a step by step basis throughout a sequence of operations in the classifier.

It is a further object to provide a rotary classifier wherein the flow of gaseous fluid carrying particles of varying sizes enters the classifier peripherally and circulatesin the form of a rotating vortex or torus within the classifying section.

It is a further object of the invention to provide a classifier wherein after the particles of varying particle sizes .are entered peripherally into an annular classifying chamber, they are subjected to a radially outward blast of air fanned within the chamber which, due to the high centrifugal forces involved, causes the larger particles to be thrown out, the smaller particles being withdrawn through an annular orifice of lesser radius.

It is a furthertobject of the invention to provide in a classifier section an annular orifice or wier having a relatively long axial length and preferably of inwardly conv'ergentor conical configuration.

It is another object of the invention to provide in a classifier system an annular classifying zone wherein the gaseous flow having a mixture of sizes of solid particles therein is maintained in a torical flow and wherein the fine si'ze particles are withdrawn through a rotating diaphragm .having' openings therein.

Other and further objects of the invention are those inherent in the apparatus herein illustrated, described and claimed.

The invention is illustrated with reference to the drawings in which corresponding numerals refer to the same parts, and wherein:

Figure l is a vertical sectional view through a grinding machine having an integral classifying apparatus'built therein and. forming a part of the combined machine;

Figure 2 is a fragmentarycross sectional view taken along the lines and in the direction of arrows 2-2 of Figure 1;

Figure 3 is a verticalsectional View of a slightly modified form of the invention;

Figure 4 is a fragmentary vertical sectional view showing another slightly modified form of the invention;

Figure 5 is a fragmentary sectional view taken along the line and in the direction of arrows 5--5 of Figure .4;

Figure 6 is a fragmentary sectional view of one of the elements shown 'in Figure 5, shown separated from the hub 46C by means of a plate 42.

" ice Figures 9, '10, 11 and 12 are each a fragmentary vertical sectional view showing slightly different modified forms of the classifying section and illustrating varying forms of slotted disk arrangements through which the fine particles are withdrawn and varying forms of the annular classifying throat of the apparatus.

Referring to Figure 1, the invention is illustrated as a part of a combined mill and classifier, the mill section being shown opposite the dimension A, and the classifier section being opposite the dimensions B and C. At the (base of the mill and as a part of the apparatus there is provided a bearing structure opposite the dimension D and a base housing opposite the dimension E, the base housing being of suitable design, depending upon the installation. Thus, the base may be composed of a fabricated or cast housing structure 1i) adapted to be supported upon any solid surface. The housing has a cover at 1'1 which forms a mounting for the entire mill and classifier structure. The housing has a wall at 12 which is provided with an aperture at i3 through which access may be had to the plurality of V-belts or other driving belts 14 which run over the pulley 15 supported on the lower end of the shaft 16. The shaft 16 is supported in a step bearing 17 of suitable mechanical design. The details of the hearing are within the province of mechanical design and, per se, form no part of the present invention. The bearing 17 is in the form of a cup housing 18 supporting a self-aligning ball or tapered roller bearing 19 which is held in place by the cap 20. Oil seals are provided at 21 and 22 and to the shaft there is attached a rotary shield at 23 which serves as a protection for the seal 22. T he bearing 11? is attached to the shaft by means of the retaining nut 24 which is adequately keyed so as to prevent loosening during operation. The cup 18 serves as a reservoir in which suitable lubricant maybe retained.

Thebase D of the mill and the mill itself is composed of an annular frame generally designated 25 which is provided with a flange at 26 by means of which it may be bolted at 27-427 to the mounting plate 11. The cylindrical shell 25 of the mill is provided with an aperture at 30 through which a current of air or other gaseous fluid, which passes through the mill, is adapted to enter, as indicated by the arrows 31-61. The course of gaseousfluid into the mill section is through an annular wier at 32 which is held in place upon the lower mill closure plate 33, the latter being firmly attached to the cylindrical wall of the mill bymeans of the flange 37.

The diaphragm or wier 32 is of relatively thin metal,

having an opening 32A, and it is held in place by aclamping ring 34 attached by the screws 35. The fiow of gaseous fluid is thus into the mill closely adjacent the shaft 16, as indicated by arrows 36-36. Immediately above the plate 33 and mounted upon the shaft 16 there is provided a fan stage at 40 which is attached to the The fan plate 42 has blading 43--43 thereon and the entering gaseous fluid is thus-impelled radially outwardly by the blading, as indicated by the arrows 44- 14. The cylindrical housing25 of the mill is usually provided with a cylindrical liner 45 of hard or resilient material, depending upon the type of grinding involved, and it may be provided with a plurality of corrugations 45A extending longitudinally of the liner.

Above the fan stage 44 there are a plurality of grinding stages, of which portions of three stages generally designated 46, 47 and 48 are shown. The mill may have any number of stages. Ea'ch stage,'in the particular mill illustrated, is composed of radial fan blades and the stages are separated by vibrating disks. Stages 46 and 47 are shown as fragments. Thus, stage has radial blades 46A; stage -47 has radial blades 47A, and-stage 48 has radial fan blades 48A. The radial blading is in each case mounted upon a suitable spoke or disk structure as at 46B for stage 46 and 483 for stage 48, the spoke or disk structure being in turn mounted upon the hub structures 46C and 48C that are pressed onto the shaft 16. Between the hubs of the successive stages are mounted the vibrating disks. Thus, between the hubs 47C and 48C is mounted the disk 49 and the supplementary supporting disks 49A. The disk 49 is resilient as are the supporting disks 49A. During the mill operation the edges of the disk 49 vibrate' axially with great intensity. Likewise, above the stage 48 and below the fan plate 52 there is mounted the vibratory disk 50 which is supported between supplementary supporting disks 50A. It will be understood that similar vibrating disks are supported between each adjacent stage of radial blading.

The construction of the rotary mill section A. per se, may be in accordance with my prior patents, such as, for example, No. 2,329,208 or No. 2,440,285, or, as illustrated, may be in accordance with the copending applications of Joseph Lecher Serial No. 213,720 filed March 3, 1951 now abandoned, and Serial No. 242,390, filed August 17, 1951.

Attention is now directed to the classifier section B of Figure 1 to which the present invention is particularly directed. The classifier section includes an enlarged annular chamber enclosed by the housing generally designated 55 and comprising the outer wall of the annular classifying chamber. Housing 55 is provided with flanges 53 and 54 at its lower and upper ends, respectively. The flange 53 is bolted to the flange 51 on the upper end of the housing 25 of the mill section. Flange 51 forms part of an inlet end wall for the inlet end of the classifying chamber. This annular flange extends toward but is spaced apart from fan plate 52 to form an annular axial inlet to the classifying chamber. The flange 54 serves as a means for bolting the upper housing plate 100 and bearing support 101 thereon. Within the housing 55 there is a plate at 56 which serves as a mounting for the annular discharge wier generally designated 57, which, according to the present invention, has a considerable axial length and may be of smooth and uniform inner diameter, as shown in Figures 11 and 12, or may be tapered inwardly in the form of a cone, as shown in Figure 10, or may be tapered inwardly in the form of a cone and .provided with steps or spiral threading, as will be referred to, the latter being illustrated in Figures 1, 3, 4 and 9. The annular classifier wier 57 is supported between the plate 56 and a lower plate 58 and is held in assembled relation by a plurality of rivets at 59. Lower plate 58 comprises an outlet end wall for the classifying chamber, being so positioned with respect to the outer wall and inner wall of the classifying chamber to form an annular outlet opening near the inner wall. Upon the shaft 16 there is provided a hub at 60 which seats upon the collar 61 which in turn'seats against the plate 52. Above the hub 60 there are a plurality of spacing collars 63 and the hub 64 of the fan section C, which is held in place by the nut 65. It will be noted that the shaft 16 has a collar at 16A adjacent the entrance wier. Accordingly, when the nut 65 is pulled down all of the hubs and various spacing collars are likewise pressed firmly against the collar 16A, thus holding the entire assembly in rigid relationship.

Upon the hub 60 there is a flange 68 to which there is attached the plate 69, which at its outer periphery is provided with a drum generally designated 70 which forms the inner wall of the annular classifying chamber. The drum 70 may have a long or short axial dimension, see, for example, Figures 1 and 3, and the lower edge of the drum rests against the plate 52. The portion of plate 52 which extends radially outwardly beyond the drum 70 serves as a mounting for the radial fan blading 71-71 which, in the form shown in Figures 1, 4 and 9 through 12, extends slightly beyond the edge 72 of the plate 52.

more closely controllable the classification will be.

Upon the upper surface of plate 69, there are provided one or more disks, of which two disks, namely disk 74 and 75 are illustrated in Figure 1. These disks are provided with apertures through them extending from a diameter which is usually slightly less than the diameter of drum 70 to the edge of the disk, or closely adjacent the edge of the disk. Referring to Figures 7 and 8 it will be noted that in the form of disk shown in Figure 7 the slots 7676 of the disk 75 extend entirely to the edge of the disk, but in some installations, particularly where high speeds are utilized and special classifying eifects are desired, the disks may simply be provided with elongated apertures more or less radially arranged, as illustrated at 77-77 in Figure 8, the outer periphery of the disks being a unitary ring at 78 which serves to strengthen the disk. The apertures 76 are preferably provided with curved inner terminations as at 76A and likewise the apertures 77 are preferably curved at 77A and at 77B.

The slotted disks are preferably made of sheer steel and the slots (or apertures) can usually be made most easily by punching or sawing. The disks can then be hard surfaced or plated, if abrasive materials are being handled.

In the form of invention shown in Figure 3, to which attention is directed, two slotted disks are provided at 80 and 81, the slotted disk 80 being of somewhat smaller diameter than 81 and chamfered at the edge. In each of Figures 9 and 10 only one disk is shown as at 39 and in each instance the disks in these figures are of the apertured type, as shown in Figure 8. In Figure 1 two slotted disks are shown, while in Figure 4 four slotted disks are illustrated, superimposed one upon the other. In Figure 11 one such slotted disk is illustrated at 41, whereas in Figure 12 three slotted disks 124126 are illustrated, said three disks being mounted in spaced relation. Thus, one or more slotted or apertured disks may be utilized and either the slotted form illustrated in Figure 7 or the apertured form illustrated in Figure 8, may be used. In general, the greater the number of slotted or apertured disks which are used in superimposed relationship, the That is to say, by stacking the slotted or apertured disks in multiple relationship, as in Figures 1, 4 or 5, the path through which the solid fine particles are withdrawn with an outflow of air is relatively much longer, and the radial centrifugal effect of the several disks, by which the coarse particles are thrown out is likewise more pronounced. Accordingly, it may be stated in general that for more closely controlled separation of particularly the finer sizes of solid particles, more slotted or apertured disks are used than where less accurate separation is desired.

As shown in Fig. 4 there are accordingly disks 82, 83, 84 and and these may be superimposed upon each other so that the slots or apertures therein are aligned with each other, or they may be superimposed so as to be staggered, as shown in Figure 5, wherein the disk 83 is rotated ahead of the disk 82 (in the direction of rotation of the device) by the amount Al, the disk 84 is rotated in the direction of rotation ahead of the disk 83 by a similar amount A2 and the disk 85 is rotated ahead of the disk 84 by the angular amount A3. Thus, in general, the path illustrated by the arrow 87 is angularly disposed upwardly and slanted in the direction of rotation of the mill. This enhances the classifying effect.

The side walls of the slots (or apertures) through the flat disks, as well as the fiat upper and lower surfaces of the disks provide surfaces to or upon which solid particles may be handled for separating the larger particles from the finer. The coarse particles are thrown radially outward along such surfaces by the action of the disks, whereas the fine particles are drawn through the slots or apertures by the gaseous fluid flow.

Referring again to Figure 1 it will be observed that the ring 58, at the lower end of the classifying wier plate aware? '57 has a maximum diameter slightly lessthanf the inside diameter of the housing 55, whereby providing a space 89 leading into the antrumor'pocket 90, which isdefined by the outer surface 57A of the wier plate 57, the under surface of the plate .56, the supporting ring 91 and a portion of the inner surface of the wall of housing 55, and the outer edge of the plate :58. The annular antrum or pocket thus formed provides a zone into which coarse particles are adapted to be received freely and from which they may later fall downwardly on the inner surface of the wall 55.

The wier plate 57, in the modification shown in Figure 1, has an inner surface of generally frustoconical shape, decreasing in diameter in the upward direction. The surface 57 is provided with a plurality of steps 57B, or steps formed as a downward screw spiral.

The flange 51 at the upper part of the mill section 25 is provided with openings 92 at several places around its periphery to which there are connected the skimmer channels 93. The lower portion of the mill housing, 25 is likewise provided with an entrance channel at 94 and with a material feed inlet at 95.

Referring to Figure 1, the section C is an integrally formed blower housing, the blower outlet being at 96. The blower consists of a ring 97 attached by cap screws to the flange of hub :64, the ring '97 being provided with a plurality of radial blades at 98-98. The entrance to the blower housing is formed by the annular aperture 56A in the center of plate 56. Upon the upper housing plate 1M there is mounted a bearing support 101 to which the hearing structure generally designated 102 is attached by means of the plate M3. The bearing 102 is similar in design to that at 17 and is provided with a drain at 104 so as to prevent any lubricant, which might seep past the seal rings 105, from entering into the rotary portions of the structure.

In operating the device shown in Figure l the gaseous fluid entering as indicated by arrows 31-31, passes through the annularwier as indicated by arrows 36, and is thence thrown outwardly by the fan blading 43-43, as shown by the arrows 44-44. Solid material to be ground, coated, mixed, separated or de-coated, separated,

, A-is reduced to fine particle size, as described in my prior patents, or in the copending applications of Joseph Lecher previously referred to. The finely divided particles carried by the gaseous fluid emerge from the grinding section A as a peripheral spiral flow, illustrated by arrows 107-107, and as they pass adjacent the fan blades 71-71 they are impinged outwardly by the flow illustrated by the arrows 108. Within the annular chamber formed by the drum 70 the housing 55 and the fan blading 71 and flange 58 at the bottom, and the rotating slotted disks 74-75 at the top, two intense torical flows are believed to take place. The lower torical flow passes in the direction of arrows 103-108, 109-109, 110 and .111. The torus the arrows 112, 113 and 114. Within the confines of the slots in disk 74 the gaseous fluid and solids carried thereby tend to be thrown outwardly, as shown by the arrows .114, and the larger. solid particles particularly are caused to be thrown radially outwardly as illustrated by the arrow 115. At the same time any solid particles thrown out may rise as shownby the arrows 116 into the annular pocket 90, from which they again emerge, as shown by arrow 117, and fall down along the inner surface of the wall 55, meanwhile being carried along rapidly by the rotation of thetorical flow about the axis of shaft 16 until they finally fall into one of the skimmer pockets 92. Since the slotted disks 74-75 rotate with the shaft 16, they are accordingly spinningat a more' rapid rate than the gaseous fluid in, torical flow in the classifying chamber in its rotation about the axis of shaft 16,. and any gaseous fluid which passes out through the ,slotsin disks 74-75 must exceed such rotary rate of travel. Thus, the flow, as indicated by arrows, 1'20 and 121, illustrates' only that flow of gaseousfluid which has been able to equal or exceed the rapid rotationof the disks 74-75. In passing through the apertures or slots in disks 74-75 the gaseous fluid and its burden of solid particles is always under centrifugal force which tends to tmove it outwardly, as shown by the arrows 114 and 115, the larger solid particles particularly being thus impelled outwardly. The result is that particle size separation takes place. The size below which the particles must be in order to be carried through the apertures orslots of the disks and thereby separated from the larger particles which are thrown centrifugally outward depends upon the, physical dimensions of the various components of the classifier, the speed of rotation and the pressure diiferential across the discharge openings constituted by the disks and wier 57. These factors can be varied by design or operation so as to enable separation at various particle size levels. Even when the flow does emerge through the slots of the disks 74-75 and into the interior space of the wier 57, it still travels in a -spiralling motion and the solid particles tend to be thrown out against the steps 5713 on such inner surface. If solid particles of appreciable size have managed topass through the slots in disks 74-75, they are still trapped bythe steps 57-57B and gradually fall or work downwardly and are tdrifted out through the clearance space between the upper slotted diskand the under surface of the plate58.

Where an increased sharpness of classification, as between particles ofclosely related sizes is desired, a greater number of slotted (orapertured) disks 82-85 are utilized, as illustrated in Figure 4, and these may be stacked in superimposed relation upon each other as shown in Figure 5, with each successively superimposed disk advanced in the direction of rotation by a certain amount which may be any dimension up to slightly less than Ithewidth of the slots or apertures in the lower disk. "The direction of rotation is shown by arrow R. The .greater the overlap dimension A1-A3 themore slanting will be the path 87 of the gaseous fluid and solid particles through through the slots, as shown in Figure 5. The :under surfaces of the superimposed disks, exposed as at 84A,85A and 86A and the adjacent edges of each slot oraperture serve as corners or ledges against which larger sizes of solid particles tend temporarily to lodge and as they lodge they are subjected to the centrifugal actionlof the rotating disks and are thrown outward beyondthe smallest dimension of the plate 58 (on the wier 57),whereupon "they are returned to the lower section of the classifier and:thence to the mill for further grinding.

Where a lesser degree of classification is desired, one slotted or apertured disk may be utilized, asshown in Figure 9, either with the step out conical discharge wier 57, or, if desired, the discharge wier 57- may have a smooth surface as at 57C in Figure 10. In some instances a sufiicient classification is obtained by-using one or more slotted disks, as shown in Figure 11, and by making the annular discharge wier 57 with a straight inner surface, as shown at 57D in Figure 11. In Figure 12 the several slotted disks, which in this instance are of the form shown in Figure 8, are mounted insspaced relationship by means of spacing washers 122-122. The

effect of such spacing is to provide anannular space at 7 gaseous flow containing several sizes of solid particles in passing through the slotted disk 124 obtains a first classification, the larger sizes of solid particles in the flow being impelled outwardly, either below the disk 124 or in the space 123 above it. The flow then passes through the slots or apertures in the disk 125 where a further classification takes place, andlikewise through the slots or apertures in disk 126 where final classification takes place. The slotted disks, in addition to being spaced apart as shown in Figure 12, may also be stacked with each successively superimposed disk advanced in the direction of rotation, as shown in Figure 5. In Figure 12 the annular classifying wier 57 may have the smooth surface of uniform diameter as at 57D or may be shaped as shown in any of the remaining figures with the step-cut surface.

Where the step-cut surface design is desired to be used, it may be built up of a plurality of disks as shown in Figure 3 or the step cut may, as in Figure 9, be cut as a spiral conical thread if desired, which spirals downwardly in the direction of rotation.

In Figure 3 several other features of the invention are illustrated. Thus, in this form of the invention the upper grinding stage 128 is set at an elevation such that the upper portion 129 of its blades act as the fan blading 71 of Figure 1, thus obviating a separate stage of fan blading. Likewise, in this modification the drum 70 has an increased axial length which, in respect to some materials, has advantage.

Also, in Figure 3, discharge ports are provided at 130 for the annular chamber 90 and separate discharge ports at 131 are provided where some of the material is desired to be withdrawn without re-grinding. In the flange surface 132 there are provided a plurality of skimmer ports 133 which may be opened or closed by adjusting the sliding .plate 134 which is held in locked position by the bolt 135 which passes through the slots 136136. The relatively large size coarse particle material which is discharged from the classifier section B falls through the tubular channel 137 into the space 138 which is defined by the housing 139140. It will be noted that in this form of the invention the entire flow of gaseous fluid into the mill is as indicated by arrow 141 which continues through the entrance wier at 142. Solid ma- -terial may be withdrawn from the mill at the opening As many apparently widely dilferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is tobe understood that I do not limit myself to the specific embodiments herein.

What I claim is:

l. A classifier for separating different sizes of solid particles comprising imperfora'te outer and inner walls which are substantially cylindrical and coaxial forming an open annular classifying chamber, said inner wall being journalled in respect to the outer wall so as to be rotatable-relative thereto, an inlet end wall for the inlet end of the chamber having an annular portion attached to one of the walls and extending toward but spaced from the other so as to form therewith an annular axial inlet into said chamber, an outlet end wall at the opposite end of said chamber positioned relative to the outer and inner wall so as to form an annular outlet opening near the inner wall, flat disk means having spaced radial apertures therein so as to leave spaced radial spokes of axial outlet,.fan means spaced apart axially from said chamber for moving a flow of gaseous fluid into said inlet and thence through said chamber and out of said outlet and an axial annular discharge wier of substantial depth between said outlet and fan means.

2. A classifier for separating different sizes of solid particles comprising imperforate outer and inner walls which are substantially cylindrical and coaxial forming an open annular classifying chamber, said innerwall being journalled in respect to the outer wall so as to be rotatable relative thereto, an inlet end wall for the inlet end of the chamber having an annular portion attached to one of the walls and extending toward but spaced from the other so as to form therewith an annular axial inlet into said chamber, an outlet end wall at the opposite end of said chamber positioned relative to the outer and inner wall so as to form an annular outlet opening near the inner wall, disk means of fiat plate having therein uniformly spaced radial slots so as to form spokes of rectangular cross section and greater width than thickness in said disk fastened to the inner wall and extending across said annular outlet opening in close proximity therewith, with said radial slots extending across said opening, fan blading mounted on and rotatable with the inner wall adjacent the inlet opening, fan means spaced apart axially from said chamber for moving a flow of gaseous fluid into said inlet and thence through said chamber and out of said outlet and an axial annular discharge wier of substantial depth between said outlet and fan means.

3. The apparatus of claim 2 further characterized in that it includes at least two layers of said fiat plate disk means mounted coaxially so as to rotate with the inner cylindrical wall, the rectangular cross section spokes of said disk means being positioned so as to extend across said annular outlet opening, the spokes of said disks being of the same in number and spacing and one disk being rotated slightly so the spokes are at least partially overlapping and advanced in the direction of rotation of said inner cylindrical wall as compared with those of the next disk means away from said outlet opening.

4. The apparatus of claim 3 further characterized in that the successive disk means are mounted in spaced relation.

5. The apparatus of claim 2 further characterized in that there are not less than three successive superimposed disk means.

6. The apparatus of claim 1 further characterized in that it includes at least two layers of relatively fiat radially slotted disks mounted so as to rotate with the inner cylindrical wall, said slots being positioned so as to extend across said annular outlet opening, the successive disks being spaced.

7. A classifier for separating different sizes of solid particles comprising, an annular classifying chamber having outer and inner cylindrical walls which are substantially coaxial, said inner cylindrical wall being journalled with respect to the outer cylindrical wall so as to be rotatable relative thereto, an inlet end wall for the inlet end of the classifying chamber having an annular portion attached to the outer cylindrical wall and extending toward but spaced from the inner cylindrical wall so as to form therewith an annular axial inlet into said chamber,-an annular outlet end wall at the opposite end of the chamber having an annular axial outlet opening there in, an annular discharge weir supported by said outlet end wall, a blower housing mounted on said classifying chamber coaxial therewith, fan blading within said housing mounted so as to be rotatable with the inner cylindrical' wall and extending toward the outer cylindrical wall parallel to the outlet for inducing a flow of gaseous fluid across said annular outlet opening, an annular'antrurn formed in the space between the outer marginal edge of the annular outlet end wall, the annular discharge weir and the outer cylindrical wall, a space between the inner marginal edge of said annular discharge Weir and said inner cylindrical wall forming said annular outlet opening from said chamber, and relatively flat rectangular cross-sectioned spokes mounted in uniformly radially spaced relation in a plane and so as to rotate with the inner cylindrical wall, said spokes being positioned so as to extend across said annular outlet opening closely adjacent thereto.

8. A classifier for separating different sizes of solid particles comprising an inner cylinder nested coaxially within an imperforate outer cylinder and journalled for rotation therein forming an open annular classifying chamber, an end wall adjacent one end of the cylinders and partially closing the space therebetween and forming an annular inlet passage into said space, a closure for the opposite end of the chamber having an annular axial outlet therein adjacent the inner cylinder, fan blading mounted for rotation with the inner cylinder adjacent said inlet and positioned so as to induce a flow of gaseous fluid in the space between said cylinders across said annular inlet, a'

flat uniformly radially slotted disk having spokes of rectangular cross section between the slots mounted so as v to rotate with the inner cylinder and in a position such that the spokes extend across and closely adjacent the annular outlet passage and an annular axial discharge wier of substantial depth in direct communication with said outlet passage.

9. A classifier for separating different sizes of solid particles comprising an annular classifying chamber composed of an inner cylinder nested coaxially within an outer cylinder and journalled for rotation therein, an end wall adjacent one end of the cylinders and partially closing the space therebetween and forming an annular inlet passage into said space, a closure plate for the opposite end of the casing having an annular axial outlet therein adjacent the inner cylinder, fan blading mounted for rotation with the inner cylinder and positioned so as to induce a flow of gaseous fluid in the space between said cylinders across said annular outlet passage, a flat disk having radial slots extending to the edge thereof, the space between the slots forming spokes, said disk being mounted so as to rotate with the inner cylinder and in a position such that the spokes extend across the annular outlet passage closely adjacent thereto, and an annular discharge weir having an inner diameter sub stantially equalling that of the annular outlet, said dis charge weir being connected to the closure plate adjacent the outlet and arranged concentrically with said outlet and extending beyond and forming a continuation of said outlet.

10. A classifier for separating different sizes of solid particles comprising an annular classifying chamber having an inner cylinder nested coaxially within an outer cylinder and journalled for rotation therein, an end wall adjacent one end of the cylinders and partially closing the space therebetween and forming an annular inlet passage into said space, an outlet closure plate at the other end of the cylinders having an annular axial outlet therein, fan blading mounted for rotation with the inner cylinder and positioned so as to induce a flow of gaseous fluid in the space between said cylinders across said an nular outlet, a flat disk radially slotted so as to have spokes of rectangular cross section between the slots, said disk being mounted so as to rotate with the inner cylinder and with the rectangular cross section spokes extending across the annular outlet passage, and an annular discharge weir with aconically convergent axial outlet having its maximum diameter substantially equalling that of the annular outlet, said discharge weir being connected to the closure plate adjacent the outlet and arranged concentrically with said outlet.

11. A classifier for separating different sizes of solid particles comprising an annular classifying chamber having an inner cylinder nested coaxially within an outer cylinder and journalled for rotation therein, an end wall adjacent one end of the cylinders and partially closing the space therebetween and forming an annular inlet passage into said space, a closure plate for the other end of the chamber having an annular axial outlet therein, fan blading mounted for rotation with the inner cylinder and positioned so as to induce a flow of gaseous fluid in the space between said cylinders across said annular outlet, a flat disk having radial slots and spokes of rectangw outlet, said discharge weir being connected to the closure plate adjacent the outlet and arranged concentrically with said outlet, said conical outlet having steps on the inner surface thereof when considered in section. V

12. A classifier for separating difierent sizes of solid particles comprising an annular classifying chamber composed of an inner cylinder nested coaxially within an outer cylinder and journalled for rotation therein, an end wall adjacent one end of the cylinders and partially closing the space therebetween and forming an annular inlet passage into said space, a closure plate for the other end of the casing having an annular axial outlet therein, fan blading mounted for rotation with the inner cylinder and positioned so as to induce a flow of gaseous fluid in the space between said cylinders across said annular outlet, 21 fiat disk uniformly radially slotted having spokes of rectangular cross section between the slots, the disk being mounted so as to rotate with the inner cylinder and position with the spokes extending across the annular outlet passage, and an annular discharge weir with a conically convergent axial outlet having its maximum diameter substantially equalling that of the annular outlet, said discharge weir being connected to the closure plate adjacent the outlet and arranged concentrically with said outlet, said conical axial outlet having a spiral groove internal thread on the interior thereof which thread has a lead towards the larger diameter end of the outlet, rota tion of said groove thread corresponding to rotation of said inner cylinder when in operation.

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Great Britain July 19, 1934 r 

